1. Field of the Invention
The present invention relates to a fuel cell vehicle. More specifically, the present invention relates to a fuel cell vehicle capable of improving energy efficiency by reducing switching loss.
2. Related Art
In recent years, fuel cell systems have attracted attention as a power source for vehicles. A fuel cell system has, for example, a fuel cell that generates electric power by causing a reactive gas to react chemically, a reactive gas supply device that supplies the fuel cell with the reactive gas via a reactive gas flow channel, and a control device that controls the reactive gas supply device.
The fuel cell has a stack structure in which, for example, several tens to several hundreds of cells are stacked. Each of the cells is configured by sandwiching a membrane electrode structure (MEA) between a pair of separators. The membrane electrode structure is configured with two electrodes (an anode (positive) and a cathode (negative)) and a solid polymer electrolyte film.
A hydrogen gas as a reactive gas is supplied to the anode of the fuel cell, while air-containing oxygen is also supplied as another reactive gas to the cathode. An electrochemical reaction thus occurs, thereby generating electric power. Basically, only neutral water is produced at the time when electric power is generated as described above. Fuel cells have, therefore, attracted attention from the viewpoints of environmental impact and use efficiency.
In a fuel cell vehicle equipped with a fuel cell system as described above, direct current power generated by the fuel cell is converted by an inverter into alternating current power, which is supplied to a motor and accessories. Between the fuel cell and the inverter, a diode is arranged with the forward direction of the diode oriented in a direction from the fuel cell toward the inverter, in order to prevent current from flowing from the inverter toward the fuel cell.
In the fuel cell vehicle, the motor and accessories require less electric power when the vehicle is stopped and idling than when the vehicle is traveling. A battery system has, therefore, been proposed that steps up voltage of an inverter to be higher than that of a fuel cell when the vehicle has been stopped and idling (for example, see Unexamined Japanese Patent Application, First Publication No. 2005-197030. According to the proposed fuel cell system, current is prevented from flowing toward the motor or accessories from the fuel cell through the inverter, by stepping up the voltage of the inverter to be higher than that of the fuel cell. Accordingly, energy efficiency is improved.